Switching power supplies such as buck or buck-boost converters operate based on the cyclic charge and discharge of an inductor. The control of the charge and discharge phase often relies on a pair of power transistors, a first transistor being used for charging the inductor and a second transistor being used for discharging it. Such systems rely on a careful timing operation of the transistors; when one transistor is open the other is closed and vice versa.
When a transistor is switched ON, a gate-source voltage of the transistor rises. Similarly, when the transistor is switched OFF, the gate-source voltage falls. Power transistors often display significant parasitic inductances and capacitances at their gate, source and drain. This can result in significant variations of the gate-source voltage during switching times and lead to the occurrence of short circuits.
To mitigate this problem, a delay also referred to as dead-time, may be introduced between the switching of the first transistor and the switching of the second transistor. In addition, one can apply a slow slew rate during the whole transient period of the transistor. Although this method can improve the noise level by reducing voltage fluctuations it also reduces efficiency by increasing the dead-time.